Methods and Systems for Creating Assemblies

ABSTRACT

Systems and methods for creating assemblies are described. One method described comprises providing a first element at a first temperature, providing a second element at a second temperature lower than the first temperature, coupling the first and second elements to create an assembly, and changing the first temperature to a third temperature, thereby preloading and interlocking the assembly. The first element comprises a first dimension at the first temperature. The second element comprises a second dimension lesser than the first dimension at the second temperature. The first element comprises a third dimension at the third temperature lesser than the first dimension.

RELATED APPLICATIONS

This application is a divisional application under 35 U.S.C. §120 ofU.S. patent application Ser. No. 10/806,603, filed Mar. 23, 2004,entitled “Methods and Systems for Creating Assemblies” and claims thebenefit under 35 U.S.C. §119(e) of U.S. Provisional Application No.60/456,412, filed Mar. 24, 2003, entitled “Thermally Activated Snap Fitand Interlock Connections.” The entire contents of U.S. patentapplication Ser. No. 10/806,603 and U.S. Provisional Application No.60/456,412 are incorporated by reference herein in their entireties.

FIELD OF THE INVENTION

The invention relates generally to methods and systems for creatingassemblies. It also relates generally to the field of engineeredstructures.

BACKGROUND

Snap-together coupling of elements is used extensively in theconventional fabrication of plastic assemblies in which elastic anddynamic performance requirements may not be high. In conventionalsnap-together couplings, there are design clearances that allow elementsto be coupled. The required design clearances in such conventionalsnap-fit couplings may create rattles and movement in the coupledassembly, and may prevent the creation of strong couplings.

Shrink-fit couplings are used in engineering practice to fasten metalelements together. Shrink-fitting is generally accomplished by firstelevating the temperature of one element to increase its physicaldimensions, then fitting a second element inside the first, and finallycooling the assembly to shrink the first element. The second elementbecomes bound by friction inside the first. This type of conventionaltechnique is used in a variety of mechanical systems, including gear andpropeller placement on shafts, and in toolholders for machine tools.Shrink fitting is normally a permanent method by which to coupleelements, and is therefore usually not reversible.

There exists a need for a method to couple elements to create strongassemblies with no or minimal play or clearance between the elements,yet using a minimal amount of time, effort, and energy to perform thecoupling.

SUMMARY OF THE INVENTION

The invention provides products and processes for creating assemblies.In one embodiment, a first element comprising an initial dimension isheated to a first temperature sufficient to expand the initial dimensionto a first dimension. The first element is then coupled with a secondelement comprising a second dimension at a second temperature. Thesecond dimension is greater than the initial dimension and lesser thanthe first dimension. The coupled first and second elements create anassembly. The coupled first element is cooled to a third temperature.Upon cooling, the first dimension of the first element is prevented fromcontracting to the initial dimension by the presence of the secondelement. The first element comprises a third dimension at the thirdtemperature. The first and/or second elements are subjected todeformation, preloading and interlocking the coupled assembly.

Embodiments of the present invention provide various advantages. Forexample, in an embodiment, a preloaded and interlocked assemblyeliminates clearances normally required by a snap-fit coupling, allowingfor a stronger assembly with properties approaching those of amonolithic structure. Embodiments of the present invention allow fornon-labor-intensive couplings to be made, reducing the assembly costsrequired to create strong assemblies that perform under demandingdynamic conditions.

These exemplary embodiments are mentioned not to limit the invention,but to provide examples of embodiments of the invention to aidunderstanding. Exemplary embodiments are discussed in the DetailedDescription, and further description of the invention is provided there.Advantages offered by the various embodiments of the present inventionmay be further understood by examining this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which constitute part of this specification,help to illustrate embodiments of the invention. In the drawings, likenumerals are used to indicate like elements throughout.

FIG. 1 is a schematic drawing of a first embodiment of the presentinvention at an initial equilibrium temperature.

FIG. 2 is a schematic drawing of the first embodiment of the presentinvention after part 102 has been heated to a first temperature.

FIG. 3 is a schematic drawing of the first embodiment of the presentinvention after part 102 has cooled to a third temperature.

FIG. 4 is a schematic drawing of a first element of a second embodimentof the present invention.

FIG. 5 is a schematic drawing of a second element of the secondembodiment of the present invention.

FIG. 6 is a schematic drawing of the first and second elements of thesecond embodiment of the present invention immediately after coupling.

FIG. 7 is a schematic drawing of the coupled first and second elementsof the second embodiment of the present invention after part 202 hascooled to a third temperature.

FIG. 8 is a schematic drawing of a second element of a third embodimentof the present invention.

FIG. 9 is a schematic drawing of a first element of the third embodimentof the present invention at an initial temperature.

FIG. 10 is a schematic drawing of the first element of the thirdembodiment at an elevated first temperature.

FIG. 11 is a schematic drawing of the first and second elements of thethird embodiment of the present invention immediately after coupling.

FIG. 12 is a schematic drawing of the coupled first and second elementsof the third embodiment of the present invention after part 302 hascooled to a third temperature.

FIG. 13 is a schematic drawing of a second element of a fourthembodiment of the present invention.

FIG. 14 is a schematic drawing of a first element of the fourthembodiment of the present invention at an initial temperature.

FIG. 15 is a schematic drawing of the first element of the fourthembodiment at an elevated first temperature.

FIG. 16 is a schematic drawing of the first and second elements of thefourth embodiment of the present invention immediately after coupling.

FIG. 17 is a cross-sectional view of the coupled first and secondelements of the fourth embodiment of the present invention after part402 has cooled to a third temperature.

FIG. 18 is a block diagram of a method according to an embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention include products and processes forcoupling elements to create an assembly. Various methods in accordancewith the present invention may be carried out. For example, the methodsmay be implemented in one embodiment by providing a first element at afirst temperature and a second element at a lower second temperature.The first element comprises a first dimension at the first temperature,and the second element comprises a lesser second dimension at the secondtemperature. The first and second elements are coupled to create anassembly.

In one such embodiment, the first temperature is then changed to a thirdtemperature, whereupon the first dimension contracts as a function ofthe first element's coefficient of thermal expansion until itmechanically interferes with the second element, eliminates anyclearance between the first and second elements. The first elementcomprises a third dimension at the third temperature. In one embodiment,the second temperature is changed to a fourth temperature, the secondelement comprising a fourth dimension at the fourth temperature. Thethird and fourth dimensions may be substantially equal, and either orboth of the first and second elements may be deformed where they contacteach other, preloading and interlocking the coupled assembly. In onesuch embodiment, the third and fourth dimensions are substantially equalwhen the third and fourth temperatures are substantially equal.

In one embodiment, the second temperature is substantially maintainedwhen the first and second elements are coupled. In another suchembodiment, the first and second temperatures are both substantiallymaintained when the first and second elements are coupled to create theassembly.

Only one of the two elements to be coupled need be substantially changedin temperature, though both may be substantially changed if desired. Inone embodiment, the second temperature remains substantially unchanged.In this embodiment, the first element is heated from an initialtemperature to a first temperature, coupled with the second element atthe second temperature, and then allowed to cool to a third temperature,while the second element maintains substantially the same temperature.In another such embodiment, only the second element substantiallychanges in temperature. The first and third temperatures of the firstelement are substantially equal, and after coupling with the secondelement, the first element maintains substantially the same temperature,while the second element warms from the second to the fourthtemperature.

The first element may comprise a first protrusion and a secondprotrusion in certain embodiments of the present invention. The secondelement in these embodiments may comprise a first and a second end, eachadapted to contact the first and second protrusions, respectively. Adistance between the first protrusion and the second protrusion of thefirst element may comprise the first dimension at the first temperature,and the third dimension at the third temperature. A distance between thefirst and second ends of the second element may comprise the seconddimension at the second temperature and the fourth dimension at thefourth temperature.

The first and second protrusions of the first element may besubstantially parallel or oblique to each other. Likewise, the first andsecond ends of the second element may be substantially parallel to oneanother, or may be substantially oblique. The first protrusion of thefirst element may be substantially parallel or substantially oblique tothe first end of the second element when the first and second elementsare coupled. Likewise, the second protrusion of the first element may besubstantially parallel or substantially oblique to the second end of thesecond element when the first and second elements are coupled.

The first element may further comprise a flexible beam. The firstprotrusion of the first element may be located at a free end of thebeam, and the second protrusion may create a base for the fixed end ofthe beam. In one such embodiment, the beam is adapted to allow couplingof the first and second elements by bendably flexing to permit the firstprotrusion to avoid the second element until the first and secondelements are fully coupled and the first protrusion is adjacent thefirst end of the second element.

The first and/or second elements may be fashioned from any material witha suitable coefficient of thermal expansion. For example, either or bothelements may comprise a metal with a coefficient of thermal expansion ina range between approximately 10 micrometers per degree Celsius permeter and approximately 25 micrometers per degree Celsius per meter. Forinstance, both elements may be fashioned from aluminum. Either or bothelements may also comprise a polymer with a coefficient of thermalexpansion in a range between approximately 0 micrometers per degreeCelsius per meter and approximately 1000 micrometers per degree Celsiusper meter. Many such polymers have tunable coefficients of thermalexpansion, allowing a wide variety of coefficients of thermal expansionto be achieved by varying the composition or type of the polymer.

In certain embodiments, the first element may comprise a coefficient ofthermal expansion different than that of the second element. In suchembodiments, the coupled elements may be heated or cooled to the sametemperature, but expand or contract differently due to their differingcoefficients of thermal expansion. The second element may also comprisean insulating coating adapted to allow differential heating of the firstand the second elements. In such an embodiment, the first and secondelements may be fashioned from the same material, but the coupledelements may be differentially heated, as the insulating coating of thesecond element prevents the second element from absorbing as much heatenergy as the uninsulated first element.

The present invention may be utilized to disassemble coupled elements.One such method comprises heating a first element comprising an initialdimension that is part of an assembly to a first temperature. The firsttemperature is sufficient to expand the initial dimension to a largerfirst dimension. The first element may be removed from the assembly whenthe first element reaches the first temperature. In one such embodiment,the first element may only be removed when it is at the firsttemperature.

In this way, the invention may be used to mechanically encrypt anassembly. In the case of a mechanically-encrypted assembly, the firstelement may only be removed from the assembly after being heated to afirst temperature in a particular manner, location or sequence oflocations. In one such mechanically-encrypted embodiment, the manner,location or sequence of heating required to remove the first elementfrom the assembly is not readily apparent from the appearance of theassembly. The coefficient of thermal expansion of the first element inone such embodiment may comprise a first value different than thecoefficient of thermal expansion of the assembly, which comprises asecond value.

The invention may be embodied in one method by heating a first elementcomprising an initial dimension to a first temperature. The firsttemperature is sufficient to expand the initial dimension to a greaterfirst dimension. The first element at the first temperature may becoupled with a second element at a second temperature to create anassembly. The second temperature is cooler than the first temperature.The second element comprises a second dimension at the secondtemperature. The second dimension is greater than the initial dimension,and lesser than the first dimension. The first element may be cooled toa third temperature. The third temperature is lower than the firsttemperature, and sufficient to contract the first dimension to a lesserthird dimension, preloading and interlocking the assembly.

The invention may be embodied in an alternate method by cooling a secondelement comprising an initial dimension, to a second temperature. Thesecond temperature is lower than the initial temperature, and sufficientto contract the initial dimension to a second, lesser dimension. Themethod further comprises maintaining a first element comprising a firstdimension at a first temperature, warmer than the second temperature.The first dimension is lesser than the initial dimension of the secondelement, but greater than the second dimension. The first element at thefirst temperature and the second element at the second temperature maybe coupled to create an assembly. The coupled second element is warmedto a fourth temperature. The fourth temperature is warmer than thesecond temperature, and the second dimension increases as a function ofthe coefficient of thermal expansion of the second element to a fourthdimension. The fourth dimension is greater than the second dimension,and contacts the first element, interlocking the assembly. The first andsecond elements are sufficiently deformed where they meet to preload theassembly.

One embodiment of the present invention is a system for couplingelements comprising a means for warming a first element comprising aninitial dimension to a first temperature sufficient to expand theinitial dimension to a first dimension. The system also comprises ameans for coupling the first element with a second element comprising asecond dimension greater than the initial dimension and lesser than thefirst dimension to create an assembly. The system also comprises a meansfor cooling the first element to a third temperature. The thirdtemperature is cooler than the first temperature, and is sufficientlycool to preload and interlock the assembly by causing the firstdimension to contract.

In one such system, the means for heating the first element may comprisea container of hot liquid. Other means for heating the first elementinclude a heating torch; an induction heating oven; a radiator; aheating pad; a remote heating device, or series thereof, that may becontrolled by a computer or manually; or any other suitable means forincreasing the temperature of the first element to the firsttemperature.

The means for coupling the first and second elements may comprise anymeans for directing the first and second elements toward each other.Such means include a conveyor belt, a hydraulic ram, a compressed airtool, a gravity-powered ramp or chute, a vice, or any other suitablemeans for coupling the first and second elements to create an assembly.

The means for cooling the first element to the third temperature in onesuch system may comprise an airspace at a typical room temperature of 72degrees Fahrenheit. Other means for cooling the first element to thethird temperature include a fan, a refrigerator, an ice chest, acontainer of cold liquid, or any other suitable means for cooling thecoupled assembly to the third temperature.

The present invention may also be embodied in an alternate system forcoupling elements. This system comprises a means for cooling a secondelement comprising an initial dimension to a second temperaturesufficient to contract the initial dimension to a second dimension. Thesecond dimension is lesser than the initial dimension, and lesser than afirst dimension of a first element. The system also comprises a meansfor coupling the second element with the first element to create anassembly. The system further comprises a means for warming the secondelement to a fourth temperature. The fourth temperature is warmer thanthe second temperature, and is sufficient to expand the second elementto a fourth dimension. The fourth dimension is greater than both thefirst and second dimensions. The expansion of the first element preloadsand interlocks the coupled assembly.

In one such system, the means for cooling the second element to thesecond temperature may comprise an airspace at a typical roomtemperature of 72 degrees Fahrenheit. Other means for cooling the secondelement to the second temperature include a fan, a refrigerator, an icechest, a container of cold liquid, or any other suitable means forcooling the first element to the first temperature.

The means for coupling the cooled second element with the first elementto create the assembly may comprise may comprise any means for directingthe first and second elements toward each other. Such means include aconveyor belt, a hydraulic ram, a compressed air tool, a gravity-poweredramp or chute, a vice, or any other suitable means for coupling thefirst and second elements to create an assembly.

The means for warming the second element to the fourth temperature inone such system may comprise a container of hot liquid. Other means forwarming the second element include a heating torch; an induction heatingoven; a radiator; a heating pad; a remote heating device, or seriesthereof, that may be controlled by a computer or manually; or any othersuitable means for increasing the temperature of assembly to the fourthtemperature.

The invention may be embodied in a thermal snap-fit, collet-pinfastener. In one such embodiment, the first element may comprise acollet pin adapted to be received by a second element comprising a tube.The collet pin first element may be heated to a first temperature, andcoupled with a second element by insertion into the second element tubeat the second temperature. The collet pin first element may then becooled to a third temperature, whereby it contracts as a function of itsthermal coefficient of expansion until it contacts the second element,now at a fourth temperature. The resulting mechanical interferencepreloads and interlocks the coupled fastener.

Referring now to FIG. 1, a drawing of two elements to be coupledaccording to an embodiment of the present invention is shown. The firstelement 102 is to be coupled with the second element 104 to create anassembly. In the present exemplary embodiment, first element 102 andsecond element 104 are fabricated from aluminum having a coefficient ofthermal expansion in the range of approximately 21 to approximately 25micrometers per degree Celsius per meter using computer numericalcontrolled machines with the ability to reliably and repeatably generatecomplex creations in metal with tolerances of less than approximately 25micrometers. In alternative embodiments of the present invention, othermaterials and methods of fabrication may be used to fabricate first andsecond elements 102 and 104. For instance, they could be composed of apolymer, a steel, or any other material with a suitable coefficient ofthermal expansion. Elements may be fabricated by casting, molding,forging, milling, or other methods. Preferably, such methods are capableof repeatably generating complex creations with tolerances on the orderof approximately 25 micrometers.

In the present exemplary embodiment, first element 102 has a firstprotrusion 106 and a second protrusion 108 that define a space of aninitial dimension 110. The second element 104 has a first end 112 and asecond end 114 that define a space of a second dimension 116. The seconddimension 116 is greater than the initial dimension 110, and when thefirst element 102 is at an initial temperature and the second element104 is at a second temperature equal to the initial temperature.Accordingly, first and second elements 102 and 104 may not be coupled tocreate an assembly due to mechanical interference.

Referring now to FIG. 2, the first element 102 and second element 104are shown in a process of being coupled according to the presentinvention. The first element 102 has been non-uniformly heated using aheat source 118 to a first temperature. The first temperature is warmerthan the initial temperature. The first temperature is sufficient toexpand former initial dimension 110 to a first dimension 120. Firstdimension 120 is greater than second dimension 116, forming a clearance142. The clearance 142 allows first element 102 to couple with secondelement 104 to create an assembly 122. The non-uniformly heated firstelement 102 is directed toward second element 104 until first protrusion106 is adjacent to first end 112 and second protrusion 108 is adjacentto second end 114, creating assembly 122. In alternative embodiments ofthe present invention, other means for coupling the elements 102, 104may be used, including a conveyor belt, a hydraulic ram, a compressedair tool, a gravity-powered ramp or chute, and a vice.

Referring now to FIG. 3, elements 102 and 104 are shown after the firsttemperature of the element 102 has been changed to a third temperature.The third temperature is cooler than the first temperature. In thepresent exemplary embodiment, upon first element 102's cooling to thethird temperature, first dimension 120 has contracted to third dimension150. Third dimension 150 is lesser than first dimension 120. The secondtemperature of the second element 104 has changed to a fourthtemperature. In the embodiment shown, the fourth temperature issubstantially equal to both the second and third temperatures. In otherembodiments, the fourth temperature is substantially unequal to thesecond and third temperatures. The second element 104 comprises a fourthdimension 160 at the fourth temperature. In the embodiment shown, thefourth dimension 160 is substantially equal to the third dimension 150,preloading and interlocking the assembly 122. In the embodiment shown,there is no clearance between the first and second elements 102, 104.

First protrusion 106 contacts first end 112, while second protrusion 108contacts second end 114, causing mechanical interference, interlockingthe assembly 122. Because of the mechanical interference caused by thecontraction of first element 102 upon cooling from the first temperatureto the third temperature, third dimension 150 cannot contract anyfurther towards its initial dimension 110 than fourth dimension 160without causing deformation of first element 102 and/or second element104. Thus, in the present exemplary embodiment, first element's 102cooling to the third temperature, the assembly 122 is preloaded andinterlocked, and there is no clearance or play between first element 102and second element 104. In other embodiments, assemblies createdaccording to the present method may be interlocked but not preloaded.

As shown in FIG. 3, in the present exemplary embodiment, once firstelement 102 has cooled to the third temperature, there is no clearancebetween the first protrusion 106 and the first end 112, nor is there anyclearance between the second protrusion 108 and the second end 114. Theassembly 122, composed of coupled first element 102 and second element104 will therefore behave similar to a monolithic structure with asimilar shape to the assembly 122. In a different embodiment, theassembly 122 may comprise a clearance between the first protrusion 106and the first end 112, and/or between the second protrusion 108 and thesecond end 114, so that the first and second elements 102, 104 may bemoved with respect to one another while coupled to create an interlockedassembly 122.

In an alternative embodiment of the present invention, the secondelement 104 is cooled from an initial temperature to a lower secondtemperature. The second temperature is lesser than the first temperatureof the first element 102. The second element 104 is then coupled withthe first element 102. At the second temperature, the second dimension116 of the second element 104 is lesser than the first dimension 120 ofthe first element 102 at the first temperature, facilitating thecoupling of first element 102 and second element 104 to create theassembly 122.

In another alternative embodiment, the second element 104 may be changedto a second temperature lower than the initial temperature withoutheating the first element 102. In this embodiment, the first temperatureis substantially equal to the initial temperature, and the firstdimension 120 is substantially equal to the initial dimension 110. Thesecond element 104 is cooled to a second temperature low enough suchthat the second dimension 116 decreases as a function of the secondelement 104's thermal coefficient of expansion to a dimension lesserthan the initial dimension 110 of the first element 102 at the initialtemperature. Once the assembly 122 has been created by coupling thefirst element 102 and the second element 104, the second temperature ofthe second element 104 is changed to a fourth temperature. The fourthtemperature is warmer than the second temperature, and the seconddimension 116 increases to a greater fourth dimension 160.

In this alternative embodiment, the first temperature of the firstelement 102 is changed to a third temperature. In this embodiment, thethird temperature is substantially equal to both the initial and firsttemperatures of the first element 102. The first element 102 comprises athird dimension 150 at the third temperature. In this alternativeembodiment, the third dimension 150 is substantially equal to the fourthdimension 160 of the second element 104. At the fourth temperature, thesecond element's 104 first end 112 contacts first protrusion 106 and thesecond end 114 contacts the second protrusion 108. The first element 102and/or the second element 104 deform, leaving the assembly 122 in apreloaded and interlocked state, with no clearance or play between firstelement 102 and second element 104. In another embodiment, the assembly122 comprises a clearance between the first and second elements 102,104.

Referring now to FIG. 4, a cross-sectional drawing of an alternativeexemplary embodiment of the present invention is shown. In FIG. 4, across-sectional view of a first element 202 is shown. In the embodimentshown, the first element 202 is fabricated from aluminum having acoefficient of thermal expansion in the range of approximately 21 toapproximately 25 micrometers per degree Celsius per meter using computernumerical controlled machines with the ability to reliably andrepeatably generate complex creations in metal with tolerances of lessthan approximately 25 micrometers. Other materials and methods offabrication may be used to fabricate first element 202. For instance,the first element 202 could be composed of a polymer, a steel, or anyother material with a suitable coefficient of thermal expansion.

In the embodiment shown in FIG. 4, the first element 202 has a series offirst protrusions 206, and a second protrusion 208 that comprises abase. Other embodiments may be shaped differently. For example, in oneembodiment, there may be only a single first protrusions and there maybe a plurality of second protrusions. As shown in FIG. 4, the firstprotrusions 206 and second protrusion 208 define a space of an initialdimension 210 when the first element 202 is at an initial temperature.In the embodiment shown, the first protrusions 206 are substantiallyparallel to the second protrusion 208. In alternative embodiments of thepresent invention, a first protrusion may be adapted differently. Forexample, a first protrusion may be substantially oblique orperpendicular to a second protrusion of the first element.

In the embodiment shown in FIG. 4, the first protrusions 206 are foundat the free end of a plurality of beams 224, each separated from theothers by a space 226. In other embodiments, beams fixed at both endscould be used, or no beams at all; also the space 226 could be omitted.In the embodiment shown, the beams 224 and the space 226 alternate in arepeating pattern around a central axis 228 to create a circle of agreatest protrusion diameter 230, creating a protruding collet pin(male) element that relies on mechanical interference, rather thanfriction, to securely couple with a receiving (female) element. Thedistance between one point on one of the first protrusions 206 locatedat the free ends of the beams 224 and the point on the opposite side ofthe opposing beam 224 creates a protrusion diameter 230.

Referring now to FIG. 5, a cross-sectional view of a second element 204at a second temperature is shown. The second element 204 shown isfabricated from aluminum having a coefficient of thermal expansion inthe range of approximately 21 to approximately 25 micrometers per degreeCelsius per meter using computer numerical controlled machines with theability to reliably and repeatably generate complex creations in metalwith tolerances of less than approximately 25 micrometers. In otherembodiments, other materials and methods of fabrication may be used tofabricate second element 204. For instance, second element 204 could becomposed of a polymer, a steel, or any other material with a suitablecoefficient of thermal expansion.

In the embodiment shown in FIG. 5, second element 204 comprises a firstend 212 adapted for contacting the first protrusions 206 of firstelement 202. Second element 204 also comprises a second end 214 adaptedfor contacting the second protrusion 208 of first element 202. First end212 and second end 214 define a second dimension 216 of greatermagnitude than initial dimension 210 of first element 202 as seen inFIG. 4. In the embodiment shown, first end 212 is substantially parallelto second end 214. In alternative embodiments, a first end of a secondelement may be oriented differently. For example, a first end may besubstantially oblique or perpendicular to a second end of the secondelement.

The second element 204 shown in FIG. 5 comprises a first surface 232adapted to contact first element 202 when first element 202 and secondelement 204 are successfully coupled. Second element 204 also comprisesa second surface 234. Alternative embodiments of the invention may usesecond surface 234 to contact first element 202 instead of, or inaddition to first surface 232. In the embodiment shown, second element204 comprises a cylindrical tube arranged about a central axis 228.Second end 214 comprises the base of the tube. Second surface 234comprises the tube's exterior surface. First surface 232 comprises thetube's inner surface of smallest diameter 236. Alternative embodimentsof the invention may use a different shape of second element 204 tocouple with first element 202. For example, second element 204 may beshaped as a polygon, an ellipse, or as an irregular shape.

The first end 212 comprises a ledge created between a recessed innersurface 238 of ledge diameter 240 greater than the smallest diameter 236created by first surface 232. Alternative embodiments of the inventionmay be created without using a ledge, or using multiple ledges orthreads. In the embodiment shown, smallest diameter 236 is smaller thanthe greatest protrusion diameter 230 of first element 202 as seen inFIG. 4. Accordingly, all beams 224 must deflect towards the same centralaxis 228 when first element 202 is coupled with second element 204.Alternative embodiments utilizing beams may require beams 224 to deflectaway from a central axis 228, or towards or away from a non-centralaxis.

Referring now to FIG. 6, first element 202 and second element 204 fromFIGS. 4 and 5, respectively, are shown being coupled to create anassembly 222. In the embodiment shown, when coupled, first element 202and second element 204 are arranged about the same central axis 228.Prior to coupling with second element 204, first element 202 has beenheated using an external heat source to an elevated first temperature.Any suitable heat source may be used. In the embodiment shown, the heatsource comprises a container of boiling water. Alternative embodimentsof the invention may use torch heating, induction heating, radiativeheating, a heating pad, or a remote heating device, or series thereof,which could be controlled by a computer or manually. In the embodimentshown, as a result of the temperature increase of first element 202,former initial dimension 210 has increased to new first dimension 220.First dimension 220 is greater than second dimension 216 to permitcoupling of first element 202 and second element 204 to create assembly222.

In the embodiment shown, the protrusion diameter 230 is lesser thanledge diameter 240, while still being greater than smallest diameter236, requiring all beams 224 to deflect towards central axis 228, usingthe clearance provided by space 226. Alternative embodiments of thepresent invention may use an alternative design. For example, beams 224may be required to deflect away from central axis 228 in order for firstelement 202 and second element 204 to couple to create assembly 222. Asshown in FIG. 6, first protrusions 206 do not contact the first end 212in the present embodiment, leaving a clearance 242. As first element 202cools to a third temperature lesser than the first temperature,clearance 242 will disappear. In the embodiment shown, first protrusions206 are substantially parallel to first end 212. In alternativeembodiments, a first protrusion of a first element may be orienteddifferently with respect to first end 212. For example, a firstprotrusion may be substantially oblique to a first end of a secondelement.

Referring now to FIG. 7, assembly 222 is shown after first element 202has cooled to a third temperature. The third temperature is lower thanthe first temperature. First dimension 220 has decreased to a thirddimension 250. In the embodiment shown, the first temperature of thefirst element has changed to the third temperature as a result ofexposure to 72 degree Fahrenheit air for an extended period of time. Inother embodiments the first temperature may be changed to the thirdtemperature by other suitable methods. The second element 204 haschanged to a fourth temperature. The second element 204 comprises afourth dimension 260 at the fourth temperature. In the embodiment shown,the fourth temperature is substantially equal to both the second andthird temperatures. In other embodiments, the fourth temperature issubstantially unequal to the second and third temperatures.

The fourth dimension 260 is substantially equal to the third dimension250. First protrusions 206 contact first end 212 and second protrusion208 contacts second end 214. Clearance 242 has been eliminated, and bothfirst protrusions 206 and first end 212 have been deformed. The assembly222 is thereby in a preloaded and interlocked condition. In theembodiment shown, there is no clearance or play between first element202 and second element 204. Alternative embodiments of the presentinvention may result in deformation of the second protrusion 208 and thesecond end 214, or may not comprise deformation of any element, insteadmaintaining a clearance between the first and second elements 202, 204.In the embodiment shown, the preloaded and interlocked condition inassembly 222 creates a rigid coupling. There is no slip, play orclearance between the first element 202 and the second element 204. Theyield strength of the assembly 222 is limited by the plastic yield loadof the materials the first element 202 and the second element 204 arefashioned from, rather than by friction. As such, the holding power ofsuch an assembly 222 is limited by material strength rather than byfriction between the first and second elements 202, 204.

Referring now to FIG. 8, an alternative embodiment of the presentinvention is shown. A second element 304 comprises a concave cylinder.The cylinder comprises an outer surface 312. The largest diameter 316and smallest diameter 317 of second element 304 are shown. Smallestdiameter 317 is lesser than largest diameter 316.

Referring now to FIG. 9, a first element 302 is shown. In the embodimentshown, the first element 302 comprises a cylindrical tube. The firstelement 302 comprises an inner surface 306 and an initial inner diameter310. The initial inner diameter 310 is smaller than both the largestdiameter 316 and the smallest diameter 317 as shown in FIG. 8.

Referring now to FIG. 10, the first element 302 is shown after beingheated to an elevated first temperature. In this embodiment, the firstelement 302 is heated using a heat source 318. As the first element 302experienced a rise in temperature, former initial inner diameter 310increases as a function of the first element 302's coefficient ofthermal expansion to a first inner diameter 320. The first innerdiameter 320 is greater than both the largest diameter 316 and thesmallest diameter 317 as shown in FIG. 8. In alternative embodiments ofthe present invention, the first inner diameter 320 is greater than thelargest diameter 316 but smaller than the smallest diameter 317.

Referring now to FIG. 11, an assembly 322 is shown. The assembly 322 iscreated by passing second element 304 through the first inner diameter320, thereby coupling the elements. In an alternative embodiment, thefirst element 302 is passed over the second element 304. In theembodiment shown, the first inner diameter 320 is larger than thesmallest diameter 317, leaving a clearance 342. The clearance 342surrounds the entire circumference of the second element's 304 outersurface 312.

Referring now to FIG. 12, the assembly 322 is shown after the firstelement 302 has cooled to a third temperature. The third temperature iscooler than the first temperature. As the first element 302 cools to thethird temperature, the first inner diameter 320 decreases as a functionof the first element's 302 coefficient of thermal expansion to a thirdinner diameter 350. The second temperature has changed to a fourthtemperature. The second element 304 comprises a fourth diameter at thefourth temperature. The fourth diameter is substantially equal to thethird inner diameter 350, preloading and interlocking the assembly.

In the embodiment shown, once the first element 302 has reached thethird temperature, the inner surface 306 contacts the outer surface 312substantially throughout the entire circumference of the second element304. In the embodiment shown, the clearance 342 is eliminated after thefirst element 302 has cooled to the third temperature. The first element302 and the second element 304 experience deformation caused by thecooling of the first element 302 to the third temperature. The assembly322 is thereby preloaded and interlocked. In the embodiment shown, thereis no clearance or play in the axial direction between first element 302and second element 304.

In FIGS. 13-17, another embodiment of the present invention is shown.FIG. 13 shows a second element 404. The second element 404 comprises agenerally cylindrical axle. The second element 404 further comprises anouter surface 412. The second element 404 shown comprises a firstdiameter 416, and a second diameter 417. The second diameter 417 islesser than the first diameter 416. The portion of the second element404 that comprises the second diameter 417 is disposed between twoportions of the second element 404 comprising the first diameter 416.The second element 404 steps down from the first diameter 416 to thesecond diameter 417, and then steps back up to the first diameter 416.In another embodiment, the second element 404 comprises chamfered edgesbetween the portion of the second element 404 comprising the seconddiameter 417 and the portions comprising the first diameter 416.

Referring now to FIG. 14, a first element 402 is shown. The firstelement 420 shown is at an initial temperature. The first element 402shown comprises a tube. The first element 402 comprises an inner surface406. The inner surface 406 comprises an inner diameter 410. The innerdiameter 410 shown in FIG. 14 is smaller than either the first diameter416 or the second diameter 417 of the second element 402 shown in FIG.13.

FIG. 15 shows the first element 402 after it has been heated to anelevated first temperature. The first temperature is greater than theinitial temperature. The first element 402 is heated using a heat source418, such as an oven. As the first element 402 experiences a rise intemperature, inner diameter 410 grows to a first inner diameter 420 as afunction of the first element's 402 coefficient of thermal expansion.The first inner diameter 420 is larger than the initial inner diameter410. The first inner diameter 420 is also larger than both the firstdiameter 416 and the second diameter 417 of the second element 404 asshown in FIG. 13.

As shown in FIG. 16, the first element 402 at the first temperature asshown in FIG. 15 has been coupled with the second element 404. Thecoupled first and second elements 402, 404 form an assembly 422. In theembodiment shown, the assembly 422 is created by passing the firstelement 402 at the elevated first temperature over the second element404, where the second element 404 is adjacent the inner surface 406. Thefirst and second elements 402, 404 are thereby coupled. The first innerdiameter 420 of the first element 402 is larger than the second diameter417 of the second element 404, leaving a clearance 442 between the firstand second elements 402, 404 around the circumference of the secondelement's 404 outer surface 412.

Referring now to FIG. 17, a cross-sectional view of the coupled firstand second elements 402, 404 is shown. The first element 402 shown hascooled to a third temperature. The third temperature is cooler than thefirst temperature. As the first element 402 cools to the thirdtemperature, the first inner diameter 420 as shown in FIGS. 15 and 16decreases as a function of the first element's 402 coefficient ofthermal expansion to a third inner diameter 450. The third innerdiameter 450 is lesser than the first inner diameter 420 and the firstdiameter 416 of the second element 404. In the embodiment shown, thethird inner diameter 450 is also lesser than the second diameter 417 ofthe second element 404, leaving the coupled assembly in a preloadedstate. The second element 404 shown comprises a fourth temperature. Thesecond diameter 417 shown in FIGS. 13 and 16 has decreased to a fourthdiameter at the fourth temperature. The fourth diameter is substantiallyequal to the third inner diameter 450.

In the embodiment shown in FIG. 17, once the first element 402 hasreached the third temperature, the inner surface 406 contacts the outersurface 412 substantially throughout the entire circumference of theportion of the second element 404 originally comprising the seconddiameter 417 as shown in FIG. 13. The shrinking of the first element 402as it cools to the third temperature has eliminated the clearance 442.In the embodiment shown, the first and second elements 402, 404experience deformation caused by the cooling of the first element 402 tothe third temperature. The assembly 422 is thereby preloaded andinterlocked. In another embodiment, the third inner diameter 450 issubstantially equal to, or greater than, the second diameter 417 of thesecond element 402 as shown in FIG. 13. In such an embodiment, the firstelement 402 generally may be free to rotate around the second element404 when the first and second elements 402, 404 are coupled. The firstelement 402 would not be free to move substantially in the axialdirection of the second element 404 in such an embodiment, as the stepsup to the first diameter 416 on either side of the portion of the secondelement 404 provide mechanical interference, interlocking the first andsecond elements 402, 404. In the embodiment shown, it is not possible tomove the first element 402 in any direction with respect to the secondelement 404.

The first element 402 shown in FIG. 17 is prevented from moving in theaxial direction and is interlocked by mechanical obstruction on eitherside by the steps up to the first diameter 416 of the second element404. In one embodiment, in order that the first element 402 fit betweenthe steps of the second element 404, the first element 402 must benarrower in the axial direction than the distance between the steps ofthe second element 404. In one embodiment, when the first element 402 isheated to the third temperature, its width in the axial directionincreases as a function of its coefficient of thermal expansion. In suchan embodiment, the distance between the steps of the second element 404may be greater than the increased width in the axial direction of thefirst element 402 at the third temperature to facilitate theinterlocking of the first and second elements 402, 404. In such anembodiment, as the first element 402 cools to the third temperature, thewidth of the first element 402 in the axial direction will decrease as afunction of the coefficient of thermal expansion. The first and secondelements 402, 404 will then be interlocked to form the assembly 422 bythe mechanical interference caused by the steps of the second element404. In such an embodiment, there may be some clearance or play in theaxial direction of the assembly 422 if there is no preloading of thefirst and second elements 402, 404.

Referring now to FIG. 18, a block diagram of a method 1800 according toan embodiment of the invention is shown. FIG. 18 shows an embodiment ofa method that may be used to couple elements to create an assembly, asdescribed above. However, the method 1800 may further be used to createalternate assemblies or couplings. The items shown above in FIGS. 1-12,as well as the accompanying description above, are referred to indescribing FIG. 18 to aid understanding of the embodiment of the method1800 shown. However, a user of the method 1800 described is not limitedto the embodiments described above and with reference to FIGS. 1-12.

As indicated by block 1805, the method 1800 shown comprises providing afirst element comprising a first dimension at a first temperature. Inone embodiment, the first element is a collet pin fashioned fromaluminum. In this embodiment, the first element is manufactured using acomputer numerical controlled machine comprising a tolerance of lessthan approximately 25 micrometers.

As indicated by block 1810, the method 1800 further comprises providinga second element comprising a second dimension at a second temperature.The second temperature is cooler than the first temperature. The seconddimension is lesser than the first dimension. In one embodiment, thesecond element is a tube fashioned from aluminum of sufficiently largeinner diameter to allow coupling with a collet pin first element. Thetube is adapted to receive a collet pin. In this embodiment, the secondelement is manufactured using a computer numerical controlled machinewith a tolerance of less than approximately 25 micrometers.

As indicated by block 1815, the method 1800 comprises coupling the firstelement at the first temperature with the second element at the secondtemperature to create an assembly.

As indicated by block 1820, the method 1800 comprises changing the firsttemperature of the first element to a third temperature, the firstelement comprising a third dimension at the third temperature. The thirdtemperature is cooler than the first temperature. In one embodiment, thefirst temperature of the first element is cooled to the thirdtemperature by exposing the coupled assembly to 72 degree Fahrenheit airfor an extended period of time.

As indicated by block 1825, the method 1800 further comprises changingthe second temperature of the second element to a fourth temperature,the second element comprising a fourth dimension at the fourthtemperature. The fourth dimension in the embodiment described issubstantially equal to the third temperature, thereby preloading andinterlocking the assembly. In one embodiment the third and fourthtemperatures are substantially equal. In one embodiment, the first andsecond elements are deformed, preloading and interlocking the assembly.

The foregoing description of the exemplary embodiments, includingpreferred embodiments, of the invention has been presented only for thepurpose of illustration and description and is not intended to beexhaustive or to limit the invention to the precise forms disclosed.Numerous modifications and adaptations thereof will be apparent to thoseskilled in the art without departing from the spirit and scope of thepresent invention.

1. A method comprising: providing a first element at a firsttemperature, the first element comprising a first dimension at the firsttemperature; providing a second element at a second temperature, thesecond temperature lower than the first temperature, the second elementcomprising a second dimension at the second temperature, the seconddimension lesser than the first dimension; coupling the first and secondelements to create an assembly; and changing the first temperature to athird temperature, the first element comprising a third dimension at thethird temperature, the third dimension lesser than the first dimension,thereby preloading and interlocking the assembly.
 2. The method of claim1, wherein coupling the first and second elements comprises maintainingsubstantially the second temperature.
 3. The method of claim 2, whereincoupling the first and second elements further comprises maintainingsubstantially the first temperature.
 4. The method of claim 1, furthercomprising: changing the second temperature to a fourth temperature, thesecond element comprising a fourth dimension at the fourth temperature,the third and fourth dimensions substantially equal.
 5. The method ofclaim 4, wherein the third and fourth temperatures are substantiallyequal.
 6. The method of claim 4, wherein the first and thirdtemperatures are substantially equal.
 7. The method of claim 1, whereinthe first element further comprises a first protrusion and a secondprotrusion, and wherein the second element further comprises a first endand a second end, the first protrusion of the first element adapted tocontact the first end of the second element, and the second protrusionof the first element adapted to contact the second end of the secondelement.
 8. The method of claim 7, wherein the first dimension of thefirst element comprises a distance between the first and secondprotrusions at the first temperature, the second dimension of the secondelement comprises a distance between the first end and the second end atthe second temperature, and the third dimension comprises a distancebetween the first and second protrusions when the first element ischanged to the third temperature.
 9. The method of claim 1, wherein thefirst element comprises a metal comprising a coefficient of thermalexpansion in a range between approximately 10 micrometers per degreeCelsius per meter and approximately 25 micrometers per degree Celsiusper meter.
 10. The method of claim 1, wherein the first elementcomprises a polymer comprising a coefficient of thermal expansion in arange between approximately 0 micrometers per degree Celsius per meterand approximately 1000 micrometers per degree Celsius per meter.
 11. Themethod of claim 1, wherein the second element comprises a metalcomprising a coefficient of thermal expansion in a range betweenapproximately 10 micrometers per degree Celsius per meter andapproximately 25 micrometers per degree Celsius per meter.
 12. Themethod of claim 1, wherein the second element comprises a polymercomprising a coefficient of thermal expansion in a range betweenapproximately 0 micrometers per degree Celsius per meter andapproximately 1000 micrometers per degree Celsius per meter.
 13. Themethod of claim 1, wherein the first element comprises a coefficient ofthermal expansion different than the second element.
 14. The method ofclaim 1, wherein the second element further comprises an insulatingcoating adapted to allow differential heating of the first and thesecond elements.